The dam is being built on the Ivindo River, near the Kongou Falls, Gabon's highest waterfall.

Mr Ona, who described the falls as "the most beautiful in central Africa", said that Gabon's government had failed to consult the local population and had not assessed the impact of the development on the environment before it gave permission for construction to begin.

He told BBC News that he hoped his receipt of the Goldman Prize would "draw international attention to just how precious this area is".

Political protest

Mr Ona, who uses a wheelchair, dedicated his early career to improving education and communication infrastructure in Gabon, including working with the United Nations Development Programme. He later turned his attention to environmental issues.

He eventually decided to focus his efforts full time on the work of his own environmental NGO, Brainforest, which aims to protect the rainforest for the benefit local of communities.

"The government established 13 national parks here, and I became interested in all the activities within them," he said.

"In 2006, my colleagues and I noticed that roads were being built within Ivindo."

The Gabonese government says it wants to encourage "eco-tourism" in Ivindo

When Mr Ona investigated, he discovered that there had been no environmental impact studies carried out before the road building started.

On its website, the Gabonese government describes the national parks as having been "classified for the conservation of Gabon's rich biodiversity".

I want to set up a clinic where the local people can be treated using traditional medicine

Marc Ona Essangui
Brainforest

The key goals of the national park scheme, it says, are preservation of "the wealth of the ecosystem for current and future generations" and stimulating "the development of ecotourism as an economic alternative to the exploitation of natural resources".

Mr Ona said: "All of this construction was carried out illegally and against the code of the national parks."

He also unearthed and leaked a copy of the Belinga mine project agreement between the government and CMEC, revealing that CMEC had been offered a 25-year tax break as part of the deal.

"When we really started to look into the deal, we noticed that it was China, not Gabon, that was the major beneficiary," he said.

Under pressure

He and his colleagues embarked on their campaign, working with other environmental NGOs, holding news conferences and meeting with local communities.

"The government even motivated some protests against the NGOs involved," he recalled.

"They alleged that we were working [on behalf of] Western powers, and we received a lot of pressure to stop the campaign."

This culminated in Mr Ona being arrested and charged with "incitement to rebellion".

He was jailed by the Gabonese judicial police on 31 December 2008; but following an internationally co-ordinated campaign for his release, he was freed on 12 January 2009.

Since June 2006, however, he has been banned from travelling outside the country.

His passport was returned to him only 24 hours before he was due to travel to San Francisco for the Goldman award ceremony.

There has been no construction in Ivindo for almost a year, but Mr Ona says this has more to do with the economic crisis and the price of iron ore than with the Gabonese government backing down.

Marc Ona Essangui lives with his family in Libreville, Gabon

He has no plans to give up his quest.

"Some of the money from this award will go to the functioning of Brainforest, and the rest will be allocated to setting up small- and medium-sized businesses for local communities," he said.

"I want to set up a clinic near Ivindo where the local people can be treated using traditional medicine. Some of the money will serve to establish this health centre for all of those communities."

No fear

The organisers of the Goldman Prize describe the six winners as "a group of fearless grassroots leaders, taking on government and corporate interests and working to improve the environment for people in their communities".

Among the other 2009 recipients are Maria Gunnoe from West Virginia, US, who has faced death threats for her outspoken activism to stop destruction of the Appalachia by the coal industry.

Also rewarded are Russian scientist Olga Speranskaya, who connected NGOs across Eastern Europe and the Caucasus region to identify and safely remove toxic chemical stockpiles, and Rizwana Hasan, Bangladesh's leading environmental attorney, whose legal advocacy led to tighter regulations on the ship-breaking industry.

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